As conventional forceps used in laparoscopic surgery, there is known those with which a gripping structure, capable of opening and closing and provided at a distal end portion of a tubular shaft 1 of small diameter, is remotely manipulated to open and close at an opposite end that is a proximal portion (see, for example, Patent Literature 1). In the present description, this gripping structure at the forceps distal end portion shall be referred to as the “gripping portion” and in particular, a gripping portion having an alligator-mouth-like shape shall be referred to as an “alligator portion.” As shown in FIG. 17, with the alligator portion 2, a pair of gripping members A and B are connected to be mutually rotatable around a rotation axis of a fulcrum portion 3. More specifically, each of the gripping members A and B has an action point portion 4 applying a force for gripping on an object to be gripped and a power point portion 5 to which the force for gripping is applied from the manipulating side. Also, at the action point portions 4, grooves for gripping the object favorably are provided as necessary on object-facing surfaces 4a and 4b that directly contact the object. With such an arrangement, when a force for opening/closing is applied from the opposite end, which is the proximal portion, to the power point portions 5 using a wire (inserted member) 7, etc., coupled to a handle 6, the gripping members A and B, for example, rotate around the rotation axis of the fulcrum portion 3 and close to enable gripping of the object.
The above-described forceps are used in various processes where an object deep inside a narrow gap needs to be gripped. For example, such forceps are useful in laparoscopic surgery (see, for example, Patent Literature 2). In a laparoscopic surgery described in Patent Literature 2, a plurality of communicating tubes called trocars are penetrated through an abdominal wall and inserted into an abdominal cavity, the interior of the abdominal cavity is observed as a monitor image using a compact camera (endoscope) inserted from one of the trocars, and while viewing the monitor image, various surgical procedures are performed inside the abdominal cavity using instruments, such as forceps, scissors, scalpel, needle holder, etc., inserted through the other trocars.
As forceps used in such laparoscopic surgery, general forceps, with the diameter of the tubular shaft being approximately 5 mm, and small-diameter forceps, with the diameter of the tubular shaft being approximately 2 mm, are known. Ordinary forceps are inserted in a trocar, for example, with a diameter of approximately 5 mm. Small-diameter forceps are inserted in a small-diameter port (trade name: Mini-Port) with a diameter of approximately 2 mm (more specifically, 2.4 mm).